Nodding syndrome may be caused by immune responses to parasite

View:170 Time:2017-02-16

Described in Science Translational Medicine, a study provides clues to the pathogenesis of Nodding syndrome, a unique seizure disorder affecting children in certain countries in East Africa. The study was conducted by investigators from the USA and Uganda.

Nodding syndrome is an unexplained neurologic condition characterized by head nodding. The disorder predominantly affect children between the ages of 5 and 15. Affected children experience a stunting of growth, leading to metal problems. When the children begin to eat or when they feel cold, they often develop nodding seizure. The effect of the disorder on families and communities can be devastating.

It has been established that the parasite Onchocerca volvulus is linked with Nodding syndrome. But the exact mechanism underlying this link remains an enigma. Onchocerca volvulus is known to cause onchocerciasis, or called river blindness, and it is transmitted from human to human by the bites of black flies.

To elucidate the connection between Onchocerca volvulus and Nodding syndrome, a team led by Avindra Nath from National Institutes of Health (USA) analyzed serum samples from both Nodding syndrome patients and healthy people in Uganda, by using protein chip methodology. Higher levels of antibodies to leiomodin-1 were detected in Nodding syndrome patients than in controls. Moreover, leiomodin-1 antibodies were found in the cerebrospinal fluid of patients.

Leiomodin-1, a protein that seems to influence cell shape, has been found in smooth muscle and thyroid cells. But this study revealed that it is also expressed in the nervous system. The discovery was confirmed by an examination of brain tissue.

Furthermore, the investigators found that antibodies that bind to leiomodin-1 are capable of binding proteins from Onchocerca volvulus, indicating that certain Onchocerca volvulus proteins resemble leiomodin-1. Based on the findings, the investigators assumed that when the body produces antibodies to fight the parasite, these antibodies may mistakenly attack neurons due to the similarities between an Onchocerca volvulus protein and leiomodin-1.

Notably, one-third of healthy controls also had leiomodin-1 antibodies. More research is required to uncover the precise function of leiomodin-1 in healthy people. A better understanding of leiomodin-1 is important to elucidate the mechanism of Nodding syndrome and other neurological disorders. The study does not prove Onchocerca volvulus is the culprit, but it supports the idea that Nodding syndrome may be an autoimmune disorder.

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